1. Field of the Invention
The present invention relates to a fixed structure of an eccentric rod and a vibration generator, and more particularly, it relates to a fixed structure of an eccentric rod generating vibration by rotation of the eccentric rod and a vibration generator.
2. Description of the Background Art
With reference to FIGS. 8 and 9, an electric toothbrush 1 is described as an example of a vibration generator. Electric toothbrush 1 employs a general fixed structure of an eccentric rod. A structure similar to electric toothbrush 1 is disclosed in Japanese Patent Laying-Open No. 2009-240155 (Patent Document 1).
Mainly referring to FIG. 9, general electric toothbrush 1 includes a case 10, a motor 20, an eccentric rod 30, a stem 40 and an oral hygiene member 50. Case 10 is tabularly formed. Case 10 is grasped by the user of electric toothbrush 1. An operating portion 13 is provided on the surface of case 1.
Motor 20 is stored in a portion close to a first end 11 of case 10. Motor 20 has a driving shaft 21. Motor 20 is connected to a prescribed power source (not shown) stored in case 10, in order to rotate driving shaft 21. Eccentric rod 30 is formed substantially in a bar-shaped manner. Eccentric rod 30 has a weight portion 33b. The barycentric position of weight portion 33b deviates from a central axis 30t of eccentric rod 30 outward (downward in the plane of FIG. 9). In other words, weight portion 33b is eccentric to central axis 30t of eccentric rod 30. The side of a second end 32 of eccentric rod 30 is connected to driving shaft 21.
Stem 40 is formed in a cap-shaped manner. A bearing portion 44 is provided inside a portion of stem 40 closer to a first end 41. A first end 31 of eccentric rod 30 is inserted into bearing portion 44. Stem 40 is mounted on the side of case 10 to cover eccentric rod 30. Oral hygiene member 50 has a tubular portion 51 and a toothbrushing portion 52. Tubular portion 51 of oral hygiene member 50 is mounted on the outer side of stem 40.
Action of electric toothbrush 1 constituted in the aforementioned manner is described. The user operates operating portion 13 to drive motor 20. Motor 20 rotates driving shaft 21. Eccentric rod 30 rotates integrally with driving shaft 21, due to power transmitted from driving shaft 21.
Weight portion 33b rotates on central axis 30t, whereby centrifugal force is generated around central axis 30t. This centrifugal force vibrates stem 40. The vibration of stem 40 is transmitted to toothbrushing portion 52 through tubular portion 51 of oral hygiene member 50. Thus, toothbrushing portion 52 vibrates.